1. Field of the Invention
The present invention relates generally to a lens device, and more particularly to a lens device for an electronic still camera.
2. Description of Related Art
A lens frame holding a lens is provided in a lens barrel. There are two methods of supporting the lens along an optical axis in the lens barrel.
In the first method, three projections are arranged on the outer periphery of the lens frame at regular intervals, and three grooves are formed along the optical axis on the inner periphery of a fixed barrel. The projections are coupled to the grooves so that the lens frame is guided along the optical axis. In the second method, guide bars are provided along the optical axis in the lens barrel, and guide blocks are provided on the lens frame. The guide bars are coupled with the guide blocks to guide the lens frame along the optical axis.
In the former method, though the lens frame is stably supported, the operating space for the lens frame is larger than that in the latter method, and this makes the lens barrel large.
In the latter method, all the ends of the guide bars are supported in case of a fixed focus lens or a relatively simple zoom lens, but only one end of each bar is supported in case of a recent zoom lens which becomes smaller in size. As disclosed in Japanese Patent Provisional Publication No. 6-324392, the back ends of the guide bars are fixed to the back surface of the lens barrel, and the front ends of them are not supported.
However, the guide bars shake when the lens is guided, and the lens can not be stably moved. If both ends of each guide bar are supported to stably move the lens, the lens barrel is large.
It is therefore an object of the present invention to provide a small lens device that permits stable movement of a lens.
The above object can be achieved by providing a lens device, comprising: a lens barrel including a movable barrel and a fixed barrel, wherein said movable barrel moves along an optical axis with respect to said fixed barrel; a support mechanism provided within the movable barrel, said support mechanism including a cylindrical middle frame and a presser ring, wherein said middle frame is slidable within the movable barrel; a lens frame holding a lens; and a guide bar that is arranged in the lens barrel to support said lens frame holding said lens so that the lens frame slides along the optical axis, wherein one end of the guide bar is fixed to a back end of the fixed barrel, and the other end of the guide bar is supported by the support mechanism provided within the movable barrel.
The supporter may be arranged in a supporting member that moves along the optical axis in the movable barrel.
According to the present invention, the back end of the guide bar is fixed to the back end of the fixed barrel, and the other end of the guide bar is supported by the supporter provided on the movable barrel. Both ends of the guide bar are supported, and the guide bar can stably move the lens. If the supporting member can move, it does not come into contact with other members in the lens barrel.